1. Field of the Invention
This invention relates to semiconductor device fabrication, and particularly to three-dimensional structures such as nanostructures and methods of fabricating the same using a printing plate.
2. Description of Background
Substantial attention has been directed to the design, implementation, and use of three-dimensional structures having well-controlled geometries and interesting optical, electrical, and/or mechanical properties. For example, three-dimensional nanostructures can comprise chemical compositions that allow them to exhibit photovoltaic, thermoelectric, diffractive, and other properties that are superior to those of other materials. Unfortunately, current methods for fabricating such three-dimensional nanostructures utilize lithography and etch processing techniques that are very complex and expensive to perform. Further, such methods are further limited by the availability of materials that can be patterned using lithography and etch techniques.
One particular type of three-dimensional structure that has received much attention is the electronic biosensor, which monitors the progress of certain biological systems. Biosensors have been described that include an array of electrode test sites in electrical connection with a plurality of conductive leads. The electrode test sites can be formed in a semiconductor wafer using photolithography and etch processing techniques. Further, the test sites can be coupled to associated detection circuitry via transistor switches using row and column addressing techniques employed, for example, in addressing dynamic random access memory (DRAM) or active matrix liquid crystal display (AMLCD) devices.
Other types of three-dimensional structures that have received much attention are photonic crystals and photonic bandgap structures. Such structures are often fabricated as two-dimensional structures because there is no economic way to fabricate them as three-dimensional structures. However, three-dimensional photonic structures are known to be much more effective. Additional types of three-dimensional nanostructures that have received increasing attention are metamaterials and thermoelectric materials. Metamaterials include a combination of different materials arranged in a defined three-dimensional geometry that causes them to exhibit extraordinary optical properties, e.g. a negative index of refraction. For visible light applications, metamaterials can require nanoscale building blocks.
There are ongoing efforts to increase the density of electrode arrays by reducing electrode and overlying lead or contact sizes to nanometer-or micrometer-scale dimensions, thereby producing “microelectrode arrays” (MEAs). However, it has been difficult to produce MEAs with very small dimensions using current top-down semiconductor fabrication methods. For example, current photolithography and etch techniques can be employed to pattern openings or vias in an insulation layer formed above the electrodes before filling those vias with a conductive material to form contacts to the electrodes. However, the ability of the photolithography and etch techniques to pattern small features is restricted by factors such as the resolution limits of the optical lithography system.
It is therefore desirable to develop a less demanding, inexpensive method for producing a large number of three-dimensional structures, particularly structures of small dimensions such as photonic crystals, nanostructures, metamaterials, microelectrode arrays, etc. It is further desirable to increase the number of materials available for forming such three-dimensional structures.